This invention relates to magnetic memory devices and in particular to a carriage movement device used in a magnetic memory device where the carriage is moved by a belt secured, without screws, to the carriage.
The field of information storage devices, and in particular, magnetic memory storage devices has developed rapidly. The need for a reliable and high speed head access mechanism has increased as the capacity of the devices has increased. The increased capacity of the memory storage device, and in particular disks of particularly high track density and high speed access have made reliable head access mechanisms essential to the proper functioning of the memory devices.
Reference is made to FIGS. 1 and 2 wherein conventional head access mechanisms are depicted. A carriage 3 which carries a head (not shown) is slidably mounted on a rod 4 by a pair of bearings 11. A capstan 1 is directly connected to a stepping motor (not shown) and is rotated in angular steps in the directions indicated by arrow A. A flexible band 2 has a slot 2a at one end. The other end of band 2 is narrower than the width of slot 2a. Band 2 is wound around capstan 1 with the other end of band 2 passing through slot 2a. Band 2 is attached to capstan 1 by a small screw 8. The other end of band 2 is attached to one end of carriage 3 using a washer 9 and a small screw 10. The one end of band 2 has a tension spring 5 and is attached to carriage 3 using a washer 6 and a small screw 7. Tension spring 5 is used to wrap band 2 around capstan 1 by providing sufficient tension to hold band 2 flatly against capstan 1. The prior art also connected band 2 without a tension spring by pulling one end of band 2 to the required tension and then attaching the end of band 2 to carriage 3.
Carriage 3 is moved in directions A' when capstan 1 is rotated in directions A by the stepping motor (not shown). As capstan 1 is angularly rotated in a stepped manner carriage 3 is linearly stepped.
However, there are several problems with the carriage movement device constructed in accordance with the prior art:
(1) When small screw 8 is tightened to fasten band 2 to capstan 1, friction in the direction of rotation of screw 8 causes a torsional force to be exerted on band 2. As a result, the uniform adhesion of band 2 to capstan 1 required for positional accuracy of carriage 3 in response to angular movement of capstan 1 is not present.
(2) When small screws 7 and 10 are tightened to securely attach band 2 to carriage 3 friction produced in the direction of rotation of screws 7, 10 through washers 6, 9 causes torsion of band 2. As a result, there is a loss of linearity of stress in band 2 in the area around small screws 7, 10. When carriage 3 moves to the right (FIG. 1) capstan 1 is closer to the portion of band 2 attached by small screw 7 and the band does not stretch linearly, while the opposite end of band 2 stretches somewhat. When carriage 3 moves to the left the same phenomenon occurs in reverse. As a result, it is not possible with this configuration to maintain the linear correlation between the linear positioning of carriage 3 and the angular stepping movement of capstan 1 required in advanced memory devices.
(3) When small screws 7, 10 are tightened in the process of attaching band 2 to carriage 3 a certain tension must be maintained in band 2. This makes assembly of the device difficult and time consuming. It is even more difficult to assemble the device when tension spring 5 is not used. One end of the band must be attached and the band stretched while the second screw is attached and tightened.
Accordingly, there is a need for a carriage movement device in a magnetic memory device which does not cause torsion of the band at the point at which it is attached to the capstan or the carriage and which is easy to assemble.